1. Field of the Invention
This invention is concerned with electrical switches, and in particular safety switches suitable, for example, for use in safety equipment associated with machinery to prevent a machine being operated when a machine guard intended for the protection of operating personnel is not properly positioned.
2. Prior Art
It is well known to provide industrial machines with safety equipment of the kind described briefly above. The equipment may include an electric switch arranged to disable the machine when the guard is not in its correct position. One form of switch in common use is a micro switch which utilizes a mechanical toggle action. However, with such switches great care is required at the design stage to ensure that the switch cannot be easily over-ridden by a machine operator to allow the machine to run in an unsafe condition.
In an attempt to avoid the drawback of mechanically operated switches it has been proposed to use a switch which is actuable by a permanent magnet. However, it has been realized that such a switch can be over-ridden with considerable ease.